(a) Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same. More particularly, the present invention relates to a diffusion barrier that blocks diffusion of metal from a metal line and a method for forming such a diffusion barrier.
(b) Description of the Related Art
During a process of manufacturing a semiconductor device, a diffusion barrier is frequently formed on an interior wall of a hole such as a contact hole or a via hole, in order to prevent diffusion of a metal such as copper from a metal line into silicon and/or an oxide.
Group-II nitrides such as tantalum nitride (TaN), in which nitrogen (N) is contained in a refractory metal such as tantalum (Ta), or group-III nitrides, such as tantalum-silicon-nitride (TaSiN) containing N and silicon (Si) together with Ta, may be used for the diffusion barrier. Among the two groups of nitrides, the group-III nitride containing Si shows better performance.
In addition, a TaSiN layer is generally easily deposited, since it is usually deposited by a physical vapor deposition (PVD) method. On the other hand, the TaSiN layer formed by the PVD method shows poor step coverage for a contact hole of a high aspect ratio. In addition, sufficient (poly)silicon remains such that, when PVD TaSiN is used as a diffusion barrier for a copper line, the copper may easily diffuse to form a copper-silicon compound or alloy (CuSi) at the interface of the TaSiN layer and the copper line layer. phenomenon during thermal processing.
For such reasons, research and investigations are conducted into forming the TaSiN layer by chemical vapor deposition (CVD), which may provide better step coverage and a (more) amorphous state for the TaSiN layer. However, according to the CVD method, the substrate has to be heated to a temperature higher than 600° C. in order to obtain a sufficient reaction between the Ta precursor and the other reaction gas(es). Therefore, the method necessarily involves a high temperature, resulting in an increase in surface roughness of the layer, and in particular, a decrease in layer density, thereby causing an agglomeration phenomenon during thermal processing.
In addition, due to various residual atoms or other materials included in the Ta precursor, an undesirable amount of impurities may be included in the layer during its deposition, thereby increasing the resistivity of the TaSiN layer.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form prior art or other information that may be already known to others in this country.